1992-08-05_GENERAL DOCUMENTS - C1980005

• Permit No: C1980005
• IBM Index Class Name: GENERAL DOCUMENTS
• Doc Date: 8/5/1992
• Doc Name: Seneca II Potential AVF Impacts
• From: Jeff Martin
• To: Susan Morrison
• Permit Index Doc Type: General Correspondence
• Email Name: SB1
• Media Type: D
• Archive: No

AVF (The first two more significant than the third or fourth) : one,
the ephemeral nature of both Bond Creek and Cow Camp Creek and
therefore the rare occurrence that discharge from either of the two
NPDES outfalls reaches Fish Creek, two, the substantially greater
flow in Fish Creek and its resultant dilution effect on water
discharged from the Seneca II mine that does manage to reach
Fish Creek, three, evapo-transpiration along the streams' alluvium
and four, the removal of surface water from Bond and Cow Camp for
stock watering.
Of utmost concern are the potential impacts Peabody may cause
when discharge from the mine site does reach Fish Creek during the
irrigation months (May, June, and/or July) and therefore the Fish
Creek AVF. An evaluation of water quality constituent
concentration levels present in the mine discharge indicates TDS
(Sulfate is the main ionic contributor - up to 86% at the outfalls)
to be the most likely to place a restriction on the quality of
irrigation water supplied to the Fish Creek AVF.
Rule 2.06.8(5) (c) (i) refers to potential increases in specific
conductance of waters supplied to an AVF as indicators of
threshold values which may be evidence of decreases in crop yields.
The USDA Handbook 60 reveals that the salinity concentration
of a soil extract would be 1.5 times the irrigation water
concentration. Therefore, orchardgrass, the most salt sensitive of
the aforementioned hay crops potentially and actually cultivated on
the Fish Creek AVF has, based on the Maas (1986) salt tolerance
publication, a surface irrigation water Specific Conductance
threshold of 1.0 mmhos/cm and a 1.5 mmhos/cm saturated soil extract
Specific Conductance threshold. In regard to the Fish Creek AVF
and Seneca II water quality data, the interest lies in irrigation
water Specific Conductance.
Some questions arise when exclusively using the salt tolerance
levels listed in the Maas publication promulgated under the
Colorado regulations, because of the great variability in the
literature regarding plant species salt tolerances under differing
environmental conditions. It is of noteworthy importance that
Peabody utilizes a different publication (Donahue, Miller,
Shickluna. An Introduction to Soils and Plant Groi&h, 1977) which
lists on page 7-252 of the permit substantially greater salt
tolerances for certain hay species (Orchardgrass saturated soil
extract threshold Specific Conductance of 2.3 mmhos/cm which
roughly corresponds to an irrigation water Specific Conductance of
1.53 mmhos/cm) . And, Peabody further maintains on page 7-253 of
the permit that because Fish Creek is in an area that experiences
a relatively cool climate where soil profiles can be kept moist
(i.e. , surface applications of water and subirrigation) even poorer
quality water may be . used without causing material damage (And
therefore even a higher irrigation water Specific Conductance than
listed above) . Peabody goes on to say (7-253) that conductivities
of irrigation water as high as 3.0 mmhos/cm may be occasionally
used without causing any detrimental effects.
3.0 mmhos/cm Specific Conductance in irrigation water is three
times the threshold level suggested by Maas (1986) of 1.0 mmhos/cm
for Orchardgrass and may be subject to review by the division.
If the division assumes that the lowest irrigation water